May be a syncro going bad. I'm not 100% sure but I would lean towards that. Check around local tanny shops and try and find one that gives free estimates. They have loads of experience and can usually tell just by driving the car.

I don't know how your engagement point would be affected by a tranny issue, but as far as reverse, I'm pretty sure that reverse gear doesn't have a synchro so if you're rolling backwards you wouldn't be able to get it in gear without some double-clutching and rev matching.